問59
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OSの機能の一つである仮想記憶方式の目的はどれか。
平成21年度 秋期 ITパスポート試験 問59
テクノロジ系ソフトウェア › オペレーティングシステム
This question's explanation and your answers so far.
解説
問 59
Incorrectア
Preventing application programs from freely accessing the main memory areas used by the OS is the function of memory protection, which has a different purpose from virtual memory. The virtual memory mechanism does help with protection as a side effect, but the purpose of the scheme is to expand capacity, not protection itself.
Incorrectイ
Writing the contents of main memory to the hard disk and then stopping the power supply in order to reduce power consumption while suspended describes hibernation. It is a power management function for saving power, and its purpose differs from that of virtual memory, which expands memory space.
- ウ
正解 The virtual memory scheme uses part of auxiliary storage (such as a hard disk) as an extension of main memory, so that programs appear to have a larger memory space than the main memory actually installed. A program runs using a continuous virtual address space, and the OS translates virtual addresses into real main memory addresses. Only the parts that are needed are kept in main memory, while parts not currently in use are moved out to auxiliary storage (paging / swapping), so even a program larger than the capacity of main memory can be executed. This is exactly what choice ウ states, and it is the very purpose of virtual memory.
Incorrectエ
Interposing memory that is faster than main memory to speed up CPU processing describes cache memory. The purpose of a cache is to close the speed gap and make processing faster, and it sits on the opposite side of the hierarchy from virtual memory (the faster, smaller-capacity side).
ここがポイント
- The purpose of the virtual memory scheme is to use auxiliary storage as an extension of main memory so that programs larger than the installed main memory capacity can be executed (paging / swapping keeps only the needed parts in main memory).
- Distinguish confusable memory-related terms: memory protection = preventing illegal access to OS areas; hibernation = saving main memory contents to disk to reduce power consumption; cache memory = speeding up processing by interposing fast memory.
用語